Multi-color light emitting carbon dots and their application in cell-imaging

Abstract

Carbon dots (C-dots), the tiny nano lights, have unfolded as an integral part of nanomaterial family in recent years. Several advantages, such as easy synthesis and purification methods from commonly available organic molecules, tunable optical properties by doping with other heteroatoms make C-dots a great biocompatible alternative to the traditional semiconductor quantum dots owing to very low toxicity and high photo stability. In this work, we report the development of a one-pot synthetic strategy for multicolor light emitting N-doped carbon dots with high quantum yields of 29% (blue c-dots), 61% (green c-dots) and 74% (yellow c-dots). These C-dots with varying nitrogen content exhibited bright and stable photoluminescence. C-dots were synthesized solvothermally from a mixture of fumaric acid and o-phenylenediamine (o-PD) in one pot and could be separated via silica column chromatography. The separated C-dots showed emission over a large spectrum of visible light from violet, blue, green, dark green, peach, light yellow and yellow fluorescence. Among these multicolored Carbon dots, the three major components, namely blue, green and yellow emissive C-dots were further characterized by spectroscopic techniques like UV-Vis, FTIR, XPS, XRD and TEM. Although the C-dots with variable emission were not different morphologically (all the C-dots are approximately 2 nm in diameter), the amount of nitrogen doping into the graphitic core varied. This resulted in varied amount of ordered packing of the alkyl groups in the core and less amount of hydrophilic surface functionalities. All the three differently emitted C-dots were employed for the in vitro imaging of cancer cells under a single-wavelength light source.